# Restructuring of Cylinder Specifications Requirements > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A96-12029 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** May 23, 1996 - **Citation:** 61 FR 25940 ## Text SUMMARY: RSPA is amending the Hazardous Materials Regulations (HMR) by restructuring the cylinder specification requirements in its regulations on Specifications for packagings. The intended effect of this rulemaking is to reduce the size of the HMR through consolidation of repetitive requirements and other formatting changes. This action eliminates approximately 45 pages of regulations from the Code of Federal Regulations without substantially changing the regulatory requirements or affecting safety. It is in response to President Clinton's March 4, 1995 Regulatory Reinvention Initiative memorandum to heads of departments and agencies calling for a review of all agency regulations. RSPA is also making corresponding reference changes throughout the HMR. DATES: Effective date: October 1, 1996. Incorporation by reference date: The incorporation by reference of certain publications listed in these amendments has been approved by the Director of the Federal Register as of October 1, 1996. FOR FURTHER INFORMATION CONTACT: John A. Gale, (202) 366-8553; Office of Hazardous Materials Standards, RSPA, Department of Transportation, Washington, DC 20590-0001. SUPPLEMENTARY INFORMATION: I. Background On March 4, 1995, President Clinton issued a Regulatory Reinvention Initiative memorandum to heads of departments and agencies calling for a review of all agency regulations and elimination or revision of those regulations that are outdated or in need of reform. RSPA has performed an extensive review of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) and associated procedural rules (49 CFR Parts 106 and 107) in response to the President's directive. The President also directed that front line regulators ``* * * get out of Washington and create grassroots partnerships'' with people affected by agency regulations. On April 4, 1995, RSPA published in the Federal Register (60 FR 17049) a Notice of Public Meetings and request for comment on its hazardous materials safety program. Comments were requested on ways to improve the HMR and the kind and quality of services its customers want. RSPA held seven public meetings and received over 50 comments in response to the notice. On July 28, 1995, RSPA published a second Notice of Public Meetings in the Federal Register (60 FR 38888) which announced five more public meetings that were held from September 1995 through January 1996. One area identified by RSPA in its review of the HMR was the need to reform the cylinder specifications in 49 CFR Part 178. On March 4, 1996 (61 FR 8328), RSPA proposed to amend the HMR by restructuring the cylinder specifications in Part 178. RSPA estimates that by consolidating duplicative requirements in 23 cylinder specifications, that it will eliminate at least 45 pages from the CFR. By reformatting the specifications, RSPA proposes to eliminate over 450 sections from Part 178 of Title 49. The combined effect of these changes will be to make the regulations shorter and easier to use and help RSPA move toward its goal of issuing the HMR in one volume of the Code of Federal Regulations, rather than two. This rulemaking also serves as the model for a comprehensive rulemaking, being developed by RSPA in cooperation with the Compressed Gas Association, for which a notice of proposed rulemaking is anticipated later this year. In this latter rulemaking, under Docket HM-220, RSPA intends to propose substantive changes to the cylinder specifications to accommodate contemporary manufacturing techniques, eliminate obsolete requirements, contemporize regulatory language and make safety enhancements to the regulations. II. Summary of Amendments RSPA received approximately 10 comments to the NPRM. All of the comments were in support of the proposal. One commenter stated that the changes proposed under Docket HM-220B are a valuable contribution to simplification of the cylinder specifications. Another commenter stated that it strongly supports the amendments proposed in Docket HM-220B to simplify and update existing regulations and to reduce the size of the HMR by consolidation of the text. Several commenters also raised concerns that were beyond the scope of the proposed rule; however, they may be considered in future rulemakings. In this final rule, RSPA is revising the HMR by restructuring the cylinder specification requirements in 49 CFR Part 178. This restructuring of the cylinder specifications: (1) consolidates similar sections; (2) reformats subpart C of Part 178 for consistency with the format of the rest of Part 178; and (3) revises section references throughout the HMR to correspond to the revised sections. RSPA intends to streamline the cylinder specification requirements without making substantive changes to them. Sections that have been consolidated are the sections of each specification addressing compliance, authorized inspectors, duties of the inspector, the inspector's report, record retention, defects, safety relief devices, and marking. These sections have been consolidated into a new Sec. 178.35. Section 178.35, entitled ``General requirements for specification cylinders'' prescribes the general requirements for all DOT specification cylinders. However, because some of the duties of the inspector and marking requirements are specific to individual cylinder designs, some specifications have additional marking and inspector requirements remaining in their sections. For the inspector's report, RSPA has adopted the inspector report formats in Compressed Gas Association (CGA) Pamphlet C-11, ``Recommended Practices for Inspection of Compressed Gas Cylinders at Time of Manufacture.'' The report formats can be modified to represent the inspection of specific cylinders. Additional information may be required as stated in each specification. In order to help facilitate transition into the new reports, RSPA is allowing inspectors an additional year, until October 1, 1997, to use the old report format required by the HMR. Those sections remaining in each specification have been consolidated into a single section. Presently, each specification is set forth in approximately 22 different sections. Under this final rule, there is only one section for each specification. For example, Specification 3B was set forth in 24 sections, Secs. 178.38 through 178.38-23. In this final rule, Specification 3B is set forth in one section, Sec. 178.38, and some of its requirements are relocated in Sec. 178.35. Sixteen of the old sections are converted to paragraphs (a) through (o) of Sec. 178.38. As an aid to the reader, the regulatory [[Page 25941]] text in this final rule includes all of the requirements for cylinders in the current Subpart C of part 178, even though not all of the requirements are changed. In response to comments, RSPA has made several changes to the original proposal. RSPA has corrected the minimum service pressure for the DOT Specification 4E cylinder to 225 psig. In the NPRM, RSPA incorrectly proposed the minimum service pressure for the 4E cylinder at 250 psig. In the NPRM, RSPA proposed to revise the marking requirements for the DOT Specification 39 to indicate that the highest monetary penalty under the Federal hazardous materials transportation law was $500,000 and not $25,000. One commenter, citing the costs of updating silk- screens, requested that RSPA not adopt this change. RSPA has not adopted this commenter's suggestion because the marking should accurately reflect the requirements of the Federal hazardous materials transportation law. However, RSPA is adding a ``grandfather'' provision for those containers marked prior to October 1, 1996. In Sec. 178.35(b)(2), RSPA is adding a reference to the DOT Specification 3E. RSPA had inadvertently left reference of that specification out of that section. The purpose of this rulemaking action is to reduce the size of the HMR and make it easier to use. It is not intended to make substantive changes to regulatory requirements and no adverse impacts are anticipated on the regulated community. III. Regulatory Analyses and Notices Executive Order 12866 and DOT Regulatory Policies and Procedures This final rule is not considered a significant regulatory action under section 3(f) of Executive Order 12866 and was not reviewed by the Office of Management and Budget. The rule is not considered significant under the regulatory policies and procedures of the Department of Transportation (44 FR 11034). The economic impact of this rule is minimal to the extent that the preparation of a regulatory evaluation is not warranted. Executive Order 12612 This final rule has been analyzed in accordance with the principles and criteria contained in Executive Order 12612 (``Federalism''). The Federal hazardous materials transportation law (49 U.S.C. 5101-5127) contains an express preemption provision that preempts State, local, and Indian tribe requirements on certain covered subjects. Covered subjects are: (i) the designation, description, and classification of hazardous material; (ii) the packing, repacking, handling, labeling, marking, and placarding of hazardous material; (iii) the preparation, execution, and use of shipping documents pertaining to hazardous material and requirements respecting the number, content, and placement of such documents; (iv) the written notification, recording, and reporting of the unintentional release in transportation of hazardous material; or (v) the design, manufacturing, fabrication, marking, maintenance, reconditioning, repairing, or testing of a package or container which is represented, marked, certified, or sold as qualified for use in the transportation of hazardous material. The Federal hazardous materials transportation law provides that if DOT issues a regulation concerning any of the covered subjects after November 16, 1990, DOT must determine and publish in the Federal Register the effective date of Federal preemption. 49 U.S.C. 5125(b)(2). That effective date may not be earlier than the 90th day following the date of issuance of the final rule and not later than two years after the date of issuance. RSPA has determined the effective date of Federal preemption for these requirements is October 1, 1996. This final rule deals with the packaging of compressed gases. Because RSPA lacks discretion in this area, preparation of a federalism assessment is not warranted. Regulatory Flexibility Act I certify that this final rule will not have a significant economic impact on a substantial number of small entities. This final rule does not impose any new requirements on persons subject to the HMR. Paperwork Reduction Act This final rule does not propose any new information collection requirements. Regulation Identifier Number (RIN) A regulation identifier number (RIN) is assigned to each regulatory action listed in the Unified Agenda of Federal Regulations. The Regulatory Information Service Center publishes the Unified Agenda in April and October of each year. The RIN number contained in the heading of this document can be used to cross-reference this action with the Unified Agenda. List of Subjects 49 CFR Part 171 Exports, Hazardous materials transportation, Hazardous waste, Imports, Incorporation by reference, Reporting and recordkeeping requirements. 49 CFR Part 173 Hazardous materials transportation, Packaging and containers, Radioactive materials, Reporting and recordkeeping requirements, Uranium. 49 CFR Part 178 Hazardous materials transportation, Incorporation by reference, Motor carrier safety, Packaging and containers, Reporting and recordkeeping requirements. In consideration of the foregoing, 49 CFR parts 171, 173, and 178 are amended as follows: PART 171--GENERAL INFORMATION, REGULATIONS, AND DEFINITIONS 1. The authority citation for Part 171 continues to read as follows: Authority: 49 U.S.C. 5101-5127; 49 CFR 1.53. 2. In Sec. 171.7(a)(3), in the table, under the entry ``Aluminum Standards and Data, Seventh Edition, June 1982'', the section reference ``178.65-5'' is revised to read ``178.46 and 178.65'', under the entry National Institute of Standards and Technology the entry for ``USDC, NBS Handbook H-28'' is amended by adding a section reference to read ``; 178.46'', under the entry American Society for Testing and Materials the entries for ASTM A 240-82, and ASTM B 557-84 are revised and two new entries are added in appropriate alpha-numerical order, and under the entry Compressed Gas Association, Inc., the entries for CGA Pamphlet C-3 and CGA Pamphlet C-12 are revised and a new entry is added in alpha-numerical order to read as follows: Sec. 171.7 Reference material. (a) * * * (3) * * * [[Page 25942]] ------------------------------------------------------------------------ Source and name of material 49 CFR reference ------------------------------------------------------------------------ * * * * * * * American Society for Testing and Materials * * * * * * * ASTM A 240-82 Standard Specification for Heat- 178.57; 178.358; 179.100; Resisting Chromium and Chromium-Nickel 179.200; 179.201; Stainless Steel Plate, Sheet and Strip for 179.220; 179.400. Fusion-Welded Unfired Pressure Vessels, Revision A. * * * * * * * ASTM B 557-84 Tension Testing Wrought and 178.46; 178.251. Cast Aluminum and Magnesium-Alloy Products. * * * * * * * ASTM E 112-88 Standard Test Methods for 178.44. Determining Average Grain Size. ASTM E 290-92 Standard Test Method for Semi- 178.46. Guided Bend Test for Ductility of Metallic Materials. * * * * * * * Compressed Gas Association, Inc., * * * * * * * CGA Pamphlet C-3, Standards for Welding and 178.47; 178.50; 178.51; Brazing on Thinned Walled Containers, 1975. 178.53; 178.54; 178.56; 178.57; 178.58; 178.59; 178.60; 178.61; 178.65; 178.68. * * * * * * * CGA Pamphlet C-11, Recommended Practices for 178.35. Inspection of Compressed Gas Cylinders at Time of Manufacture, 1993. CGA Pamphlet C-12, Qualification Procedure 173.34; 173.303; 178.59; for Acetylene Cylinder Design, 1994. 178.60. * * * * * * * ------------------------------------------------------------------------ * * * * * PART 173--SHIPPERS--GENERAL REQUIREMENTS FOR SHIPMENTS AND PACKAGINGS 3. The authority citation for Part 173 continues to read as follows: Authority: 49 U.S.C. 5101-5127; 49 CFR 1.53. Sec. 173.34 [Amended] 4. In Sec. 173.34, paragraph (h) is amended by: a. Removing, in the first sentence, the phrase ``Secs. 178.36-9(a), 178.37-9(a), 178.38-9(a), and 178.40-9(a)'' and replacing it with the phrase ``Sec. 178.36(e), 178.37(e), 178.38(e), and 178.40(e)''. b. Removing, in the fourth sentence, the phrase ``Sec. 178.36-9(a), Sec. 178.37-9(a), Sec. 178.38-9(a), or Sec. 178.40-9(a)'' and replacing it with the phrase ``Sec. 178.36(e), 178.37(e), 178.38(e), or 178.40(e)''. Sec. 173.316 [Amended] 5. In Sec. 173.316, in paragraph (a)(8), the section reference ``178.57-20(a)(4)'' is revised to read ``178.35'' and in paragraph (c)(3)(ii) the section reference ``178.57-20'' is revised to read ``178.35''. PART 178--SPECIFICATIONS FOR PACKAGINGS 6. The authority citation for Part 178 continues to read as follows: Authority: 49 U.S.C. 5101-5127; 49 CFR 1.53. 7. Subpart C of Part 178 is revised to read as follows: Subpart C--Specifications for Cylinders Sec. 178.35 General requirements for specification cylinders. 178.36 Specification 3A and 3AX seamless steel cylinders. 178.37 Specification 3AA and 3AAX seamless steel cylinders. 178.38 Specification 3B seamless steel cylinders. 178.39 Specification 3BN seamless nickel cylinders. 178.42 Specification 3E seamless steel cylinders. 178.44 Specification 3HT seamless steel cylinders for aircraft use. 178.45 Specification 3T seamless steel cylinders. 178.46 Specification 3AL seamless aluminum cylinders. 178.47 Specification 4DS welded stainless steel cylinders for aircraft use. 178.50 Specification 4B welded or brazed steel cylinders. 178.51 Specification 4BA welded or brazed steel cylinders. 178.53 Specification 4D welded steel cylinders for aircraft use. 178.55 Specification 4B240ET welded or brazed cylinders. 178.56 Specification 4AA480 welded steel cylinders. 178.57 Specification 4L welded insulated cylinders. 178.58 Specification 4DA welded steel cylinders for aircraft use. 178.59 Specification 8 steel cylinders with porous fillings for acetylene. 178.60 Specification 8AL steel cylinders with porous fillings for acetylene. 178.61 Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam. 178.65 Specification 39 non-reusable (non-refillable) cylinders. 178.68 Specification 4E welded aluminum cylinders. Subpart C--Specifications for Cylinders Sec. 178.35 General requirements for specification cylinders. (a) Compliance. Compliance with the requirements of this subpart is required in all details. (b) Inspections and analyses. Chemical analyses and tests as specified must be made within the United States unless otherwise approved in writing by the Associate Administrator, in accordance with Sec. 173.300b of this subchapter. Inspections and verifications must be performed by-- [[Page 25943]] (1) An independent inspection agency approved in writing by the Associate Administrator, in accordance with Sec. 173.300a of this subchapter; or (2) For DOT Specifications 3B, 3BN, 3E, 4B, 4BA, 4D (water capacity less than 1,100 cubic inches), 4B240ET, 4AA480, 4L, 8, 8AL, 4BW, 39 (marked service pressure 900 p.s.i.g. or lower) and 4E manufactured in the United States, a competent inspector of the manufacturer. (c) Duties of inspector. The inspector shall determine that each cylinder made is in conformance with the applicable specification. Except as otherwise specified in the applicable specification, the inspector shall perform the following: (1) Inspect all material and reject any not meeting applicable requirements. For cylinders made by the billet-piercing process, billets must be inspected and shown to be free from pipe, cracks, excessive segregation and other injurious defects after parting or, when applicable, after nick and cold break. (2) Verify the material of construction meets the requirements of the applicable specification by-- (i) Making a chemical analysis of each heat of material; (ii) Obtaining a certified chemical analysis from the material manufacturer for each heat of material (a ladle analysis is acceptable); or (iii) If an analysis is not provided for each heat of material by the material manufacturer, by making a check analysis of a sample from each coil, sheet, or tube. (3) Verify compliance of cylinders with the applicable specification by-- (i) Verifying identification of material is proper; (ii) Inspecting the inside of the cylinder before closing in ends; (iii) Verifying that the heat treatment is proper; (iv) Obtaining samples for all tests and check chemical analyses; (v) Witnessing all tests; (vi) Verify threads by gauge; (vii) Reporting volumetric capacity and tare weight (see report form) and minimum thickness of wall noted; and (viii) Verifying that each cylinder is marked in accordance with the applicable specification. (4) Furnish complete test reports required by this subpart to the maker of the cylinder and, upon request, to the purchaser. The test report must be retained by the inspector for fifteen years from the original test date of the cylinder. (d) Defects. A cylinder may not be constructed of material with seams, cracks, laminations, or other injurious defects. (e) Safety devices. Safety devices and protection for valves, safety devices, and other connections, if applied, must be as required or authorized by the appropriate specification, and as required in Secs. 173.34 and 173.301 of this subchapter. (f) Markings. Markings on a DOT Specification cylinder must conform to applicable requirements. (1) Each cylinder must be marked with the following information: (i) The DOT specification marking must appear first, followed immediately by the service pressure. For example, DOT-3A1800. (ii) The serial number must be placed just below or immediately following the DOT specification marking. (iii) A symbol (letters) must be placed just below, immediately before or following the serial number. Other variations in sequence of markings are authorized only when necessitated by a lack of space. The symbol and numbers must be those of the manufacturer. The symbol must be registered with the Associate Administrator; duplications are not authorized. (iv) The inspector's official mark and date of test (such as 5-95 for May 1995) must be placed near the serial number. This information must be placed so that dates of subsequent tests can be easily added. An example of the markings prescribed in this paragraph (f)(1) is as follows: DOT-3A1800 1234 XY AB 5-95 Or; DOT-3A1800-1234-XY AB 5-95 Where: DOT-3A=specification number 1800=service pressure 1234=serial number xy=symbol of manufacturer AB=inspector's mark 5-95=date of test (2) Additional required marking must be applied to the cylinder as follows: (i) The word ``spun'' or ``plug'' must be placed near the DOT specification marking when an end closure in the finished cylinder has been welded by the spinning process, or effected by plugging. (ii) As prescribed in specification 3HT (Sec. 178.44) or 3T (Sec. 178.45), if applicable. (3) Marking exceptions. (i) A DOT 3E cylinder is not required to be marked with the inspector mark. (ii) An identifying lot number may be marked on the cylinder in place of a serial number for cylinders not over 2 inches outside diameter or for cylinders with a volumetric capacity not exceeding 60 cubic inches. Each lot shall not have over 500 cylinders. (4) Unless otherwise specified in the applicable specification, the markings on each cylinder must be stamped plainly and permanently on the shoulder, top head, or neck. (5) The size of each marking must be at least 0.25 inch or as space permits. (6) Other markings are authorized provided they are made in low stress areas other than the side wall and are not of a size and depth that will create harmful stress concentrations. Such marks may not conflict with any DOT required markings. (g) Inspector's report. Each inspector shall prepare a report containing, at a minimum, the applicable information listed in CGA Pamphlet C-11 or, until October 1, 1997, in accordance with the applicable test report requirements of this subchapter in effect on September 30, 1996. Any additional information or markings that are required by the applicable specification must be shown on the test report. The signature of the inspector on the reports certifies that the processes of manufacture and heat treatment of cylinders were observed and found satisfactory. (h) Report retention. The manufacturer of the cylinders shall retain the reports required by this subpart for 15 years from the original test date of the cylinder. Sec. 178.36 Specification 3A and 3AX seamless steel cylinders. (a) Type size and service pressure. In addition to the requirements of Sec. 178.35, cylinders must conform to the following: (1) A DOT-3A cylinder is a seamless steel cylinder with a water capacity (nominal) not over 1,000 pounds and a service pressure of at least 150 pounds per square inch. (2) A DOT-3AX is a seamless stainless steel cylinder with a water capacity not less than 1,000 pounds and a service pressure of at least 500 pounds per square inch, conforming to the following requirements: (i) Assuming the cylinder is to be supported horizontally at its two ends only and to be uniformly loaded over its entire length consisting of the weight per unit of length of the straight cylindrical portion filled with water and compressed to the specified test pressure; the sum of two times the maximum tensile stress in the bottom fibers due to bending, plus that in the same fibers (longitudinal stress), due to hydrostatic test may not exceed 80 [[Page 25944]] percent of the minimum yield strength of the steel at such maximum stress. Wall thickness must be increased when necessary to meet the requirement. (ii) To calculate the maximum longitudinal tensile stress due to bending, the following formula must be used: S=Mc/I (iii) To calculate the maximum longitudinal tensile stress due to hydrostatic test pressure, the following formula must be used: S=A1P/A2 where: S=tensile stress--p.s.i.; M=bending moment-inch pounds--(wl2)/8; w=weight per inch of cylinder filled with water; l=length of cylinder-inches; c=radius (D)/(2) of cylinder-inches; I=moment of inertia--0.04909 (D4-d4) inches fourth; D=outside diameter-inches; d=inside diameter-inches; A1=internal area in cross section of cylinder-square inches; A2=area of metal in cross section of cylinder-square inches; P=hydrostatic test pressure-p.s.i. (b) Steel. Open-hearth or electric steel of uniform quality must be used. Content percent may not exceed the following: Carbon, 0.55; phosphorous, 0.045; sulphur, 0.050. (c) Identification of material. Material must be identified by any suitable method, except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise treated to eliminate these defects. The thickness of the bottoms of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thicknesses must be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts and only to the tops and bottoms of cylinders having a service pressure of 500 pounds per square inch or less. Cylinders, neckrings, and footrings must be made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedures. (2) As permitted in paragraph (d) of this section. (3) Cylinders used solely in anhydrous ammonia service may have a \1/2\ inch diameter bar welded within their concave bottoms. (f) Wall thickness. For cylinders with service pressure less than 900 pounds, the wall stress may not exceed 24,000 pounds per square inch. A minimum wall thickness of 0.100 inch is required for any cylinder over 5 inches outside diameter. Wall stress calculation must be made by using the following formula: S=[P(1.3D2+0.4d2)]/(D2-d2) Where: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=outside diameter in inches; d=inside diameter in inches. (g) Heat treatment. The completed cylinder must be uniformly and properly heat-treated prior to tests. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, must be of length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable methods, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus the test pressure cannot be maintained the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent, volumetric expansion may not exceed 10 percent of the total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least \5/3\ times service pressure. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) Gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length of at least 24 times thickness with width not over 6 times thickness is authorized when cylinder wall is not over \3/ 16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the [[Page 25945]] gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2-percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch and the strain indicator reading must be set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation at least 40 percent for a 2-inch gauge length or at least 20 percent in other cases and yield strength not over 73 percent of tensile strength. In this instance, the flattening test is not required. (2) An elongation at least 20 percent for a 2-inch gauge length or 10 percent in other cases and a yield strength not over 73 percent of tensile strength. In this instance, the flattening test is required, without cracking, to 6 times the wall thickness. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture subject to the following conditions and limitations: (1) Pressure, approximately the same as but no less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least 1 minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, a cylinder that is leaking must be rejected. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provisions of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. Sec. 178.37 Specification 3AA and 3AAX seamless steel cylinders. (a) Type, size and service pressure. In addition to the requirements of Sec. 178.35, cylinders must conform to the following: (1) A DOT-3AA cylinder is a seamless steel cylinder with a water capacity (nominal) of not over 1,000 pounds and a service pressure of at least 150 pounds per square inch. (2) A DOT-3AAX cylinder is a seamless steel cylinder with a water capacity of not less than 1,000 pounds and a service pressure of at least 500 pounds per square inch, conforming to the following requirements: (i) Assuming the cylinder is to be supported horizontally at its two ends only and to be uniformly loaded over its entire length consisting of the weight per unit of length of the straight cylindrical portion filled with water and compressed to the specified test pressure; the sum of two times the maximum tensile stress in the bottom fibers due to bending, plus that in the same fibers (longitudinal stress), due to hydrostatic test pressure may not exceed 80 percent of the minimum yield strength of the steel at such maximum stress. Wall thickness must be increased when necessary to meet the requirement. (ii) To calculate the maximum tensile stress due to bending, the following formula must be used: S=Mc/I (iii) To calculate the maximum longitudinal tensile stress due to hydrostatic test pressure, the following formula must be used: S=A\1\P/A\2\ Where: S=tensile stress-p.s.i.; M=bending moment-inch pounds (wl\2\)/8; w=weight per inch of cylinder filled with water; l=length of cylinder-inches; c=radius (D)/(2) of cylinder-inches; I=moment of inertia-0.04909 (D\4\-d\4\) inches fourth; D=outside diameter-inches; d=inside diameter-inches; A\1\=internal area in cross section of cylinder-square inches; A\2\=area of metal in cross section of cylinder-square inches; P=hydrostatic test pressure-p.s.i. (b) Authorized steel. Open-hearth, basic oxygen, or electric steel of uniform quality must be used. A heat of steel made under the specifications in Table 1 of this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 of this paragraph (b) are not exceeded. When a carbon-boron steel is used, a hardenability test must be performed on the first and last ingot of each heat of steel. The results of this test must be recorded on the Record of Chemical Analysis of Material for Cylinders required by Sec. 178.35. This hardness test must be made \5/16\-inch from the quenched end of the Jominy quench bar and the hardness must be at least Rc 33 and no more than Rc 53. The following chemical analyses are authorized: Table 1.--Authorized Materials -------------------------------------------------------------------------------------------------------------------------------------------------------- Inter- mediate Designation 4130X (percent) NE-8630 (percent) 9115 (percent) 9125 (percent) Carbon-boron manganese (see Note 1) (see Note 1) (see Note 1) (see Note 1) (percent) (percent) -------------------------------------------------------------------------------------------------------------------------------------------------------- Carbon.......................... 0.25/0.35......... 0.28/0.33......... 0.10/0.20......... 0.20/0.30......... 0.27-0.37......... 0.40 max. [[Page 25946]] Manganese....................... 0.40/0.90......... 0.70/0.90......... 0.50/0.75......... 0.50/0.75......... 0.80-1.40......... 1.35/1.65. Phosphorus...................... 0.04 max.......... 0.04 max.......... 0.04 max.......... 0.04 max.......... 0.035 max......... 0.04 max. Sulfur.......................... 0.05 max.......... 0.04 max.......... 0.04 max.......... 0.04 max.......... 0.045 max......... 0.05 max. Silicon......................... 0.15/0.35......... 0.20/0.35......... 0.60/0.90......... 0.60/0.90......... 0.3 max........... 0.10/0.30. Chromium........................ 0.80/1.10......... 0.40/0.60......... 0.50/0.65......... 0.50/0.65. Molybdenum...................... 0.15/0.25......... 0.15/0.25 Zirconium....................... .................. .................. 0.05/0.15......... 0.05/0.15 Nickel.......................... .................. 0.40/0.70......... Boron........................... .................. .................. .................. .................. 0.0005/0.003. -------------------------------------------------------------------------------------------------------------------------------------------------------- Note 1: This designation may not be restrictive and the commercial steel is limited in analysis as shown in this Table. Table 2.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the minimum limit Element Limit or maximum specified (percent) ------------------------- Under Over minimum maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon........................................ To 0.15 incl.......................... 0.02 0.03 Over 0.15 to 0.40 incl................ .03 .04 Manganese..................................... To 0.60 incl.......................... .03 .03 Over 0.60 to 1.15 incl................ 0.04 0.04 Over 1.15 to 2.50 incl................ 0.05 0.05 Phosphorus\1\................................. All ranges............................ ........... .01 Sulphur....................................... All ranges............................ ........... .01 Silicon....................................... To 0.30 incl.......................... .02 .03 Over 0.30 to 1.00 incl................ .05 .05 Nickel........................................ To 1.00 incl.......................... .03 .03 Chromium...................................... To 0.90 incl.......................... .03 .03 0.90 to 2.90 incl..................... .05 .05 Molybdenum.................................... To 0.20 incl.......................... .01 .01 Over 0.20 to 0.40..................... .02 .02 Zirconium..................................... All ranges............................ .01 .05 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus. (c) Identification of material. Material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defects is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise treated to eliminate these defects. The thickness of the bottoms of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thicknesses must be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts, and only to the tops and bottoms of cylinders having a service pressure of 500 pounds per square inch or less. Cylinders, neckrings, and footrings must be made of weldable steel, the carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedure. (2) As permitted in paragraph (d) of this section. (f) Wall thickness. The thickness of each cylinder must conform to the following: (1) For cylinders with a service pressure of less than 900 pounds, the wall stress may not exceed 24,000 pounds per square inch. A minimum wall thickness of 0.100 inch is required for any cylinder with an outside diameter of over 5 inches. (2) For cylinders with service pressure of 900 p.s.i. or more the minimum wall must be such that the wall stress at the minimum specified test pressure may not exceed 67 percent of the minimum tensile strength of the steel as determined from the physical tests required in paragraphs (k) and (l) of this section and must be not over 70,000 p.s.i. (3) Calculation must be made by the formula: S=[P(1.3D2+0.4d2)]/(D2-d2) Where: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=outside diameter in inches; d=inside diameter in inches. (g) Heat treatment. The completed cylinders must be uniformly and properly heat treated prior to tests. Heat treatment of cylinders of the authorized analyses must be as follows: [[Page 25947]] (1) All cylinders must be quenched by oil, or other suitable medium except as provided in paragraph (g)(5) of this section. (2) The steel temperature on quenching must be that recommended for the steel analysis, but may not exceed 1750 deg.F. (3) All steels must be tempered at a temperature most suitable for that steel. (4) The minimum tempering temperature may not be less than 1000 deg.F except as noted in paragraph (1)(vi) of this section. (5) Steel 4130X may be normalized at a temperature of 1650 deg.F instead of being quenched and cylinders so normalized need not be tempered. (6) Intermediate manganese steels may be tempered at temperatures not less than 1150 deg.F., and after heat treating each cylinder must be submitted to a magnetic test to detect the presence of quenching cracks. Cracked cylinders must be rejected and destroyed. (7) Except as otherwise provided in paragraph (g)(6) of this section, all cylinders, if water quenched or quenched with a liquid producing a cooling rate in excess of 80 percent of the cooling rate of water, must be inspected by the magnetic particle, dye penetrant or ultrasonic method to detect the presence of quenching cracks. Any cylinder designed to the requirements for specification 3AA and found to have a quenching crack must be rejected and may not be requalified. Cylinders designed to the requirements for specification 3AAX and found to have cracks must have cracks removed to sound metal by mechanical means. Such specification 3AAX cylinders will be acceptable if the repaired area is subsequently examined to assure no defect, and it is determined that design thickness requirements are met. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, must be of a length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy of either 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least \5/3\ times the service pressure. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out of each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to the same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) Gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length of at least 24 times the thickness with width not over 6 times thickness when the thickness of the cylinder wall is not over \3/16\ inch. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within 1 inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. An acceptable result for physical and flattening tests is elongation at least 20 percent for 2 inches of gauge length or at least 10 percent in other cases. Flattening is required without cracking to 6 times the wall thickness of the cylinder. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture. Pressure, approximately the same as but no less than the service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, a cylinder must be rejected if there is any leaking. [[Page 25948]] (1) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (2) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (3) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provision of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. Sec. 178.38 Specification 3B seamless steel cylinders. (a) Type, size, and service pressure. A DOT 3B cylinder is seamless steel cylinder with a water capacity (nominal) of not over 1,000 pounds and a service pressure of at least 150 to not over 500 pounds per square inch. (b) Steel. Open-hearth or electric steel of uniform quality must be used. Content percent may not exceed the following: carbon, 0.55; phosphorus, 0.045; sulphur, 0.050. (c) Identification of material. Material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise treated to eliminate these defects. The thickness of the bottoms of cylinders welded or formed by spinning is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thicknesses to be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except as follows: (1) Welding or brazing is authorized for the attachment of neckrings and footrings which are non-pressure parts, and only to the tops and bottoms of cylinders having a service pressure of 500 pounds per square inch or less. Cylinders, neckrings, and footrings must be made of weldable steel, carbon content of which may not exceed 0.25 percent except in the case of 4130X steel which may be used with proper welding procedure. (2) As permitted in paragraph (d) of this section. (f) Wall thickness. The wall stress may not exceed 24,000 pounds per square inch. The minimum wall thickness is 0.090 inch for any cylinder with an outside diameter of 6 inches. Calculation must be made by the following formula: S=[P(1.3D\2\+0.4d\2\)]/(D\2\-d\2\) Where: S=wall stress in pounds per square inch; P=at least two times service pressure or 450 pounds per square inch, whichever is the greater; D=outside diameter in inches; d=inside diameter in inches. (g) Heat treatment. The completed cylinders must be uniformly and properly heat-treated prior to tests. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads, conforming to the following, are required on all openings: (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads when used, must be of a length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 4 engaged threads are authorized. Straight threads must have a tight fit, and calculated shear strength at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Cylinders must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to insure complete expansion. Any internal pressure applied after heat-treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Cylinders must be tested as follows: (i) Each cylinder; to at least 2 times service pressure; or (ii) 1 cylinder out of each lot of 200 or less; to at least 3 times service pressure. Others must be examined under pressure of 2 times service pressure and show no defect. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) Gauge length of 8 inches with a width of not over 1\1/2\ inches; or a gauge length of 2 inches with a width of not over 1\1/2\ inches; or a gauge length at least 24 times the thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of [[Page 25949]] physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, and the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation of at least 40 percent for a 2-inch gauge length or at least 20 percent in other cases and yield strength not over 73 percent of tensile strength. In this instance, the flattening test is not required. (2) An elongation of at least 20 percent for a 2-inch gauge length or 10 percent in other cases and yield strength not over 73 percent of tensile strength. Flattening is required, without cracking, to 6 times the wall thickness. (m) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture, subject to the following conditions and limitations: (1) Pressure, approximately the same as but no less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (n) of this section, a cylinder must be rejected if there is any leaking. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, he should design his apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (n) Rejected cylinders. Reheat treatment of rejected cylinders is authorized. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provisions of paragraph (m) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. (o) Marking. Markings may be stamped into the sidewalls of cylinders having a service pressure of 150 psi if all of the following conditions are met: (1) Wall stress at test pressure may not exceed 24,000 psi. (2) Minimum wall thickness must be not less than 0.090 inch. (3) Depth of stamping must be no greater than 15 percent of the minimum wall thickness, but may not exceed 0.015 inch. (4) Maximum outside diameter of cylinder may not exceed 5 inches. (5) Carbon content of cylinder may not exceed 0.25 percent. If the carbon content exceeds 0.25 percent, the complete cylinder must be normalized after stamping. (6) Stamping must be adjacent to the top head. Sec. 178.39 Specification 3BN seamless nickel cylinders. (a) Type, size and service pressure. A DOT 3BN cylinder is a seamless nickel cylinder with a water capacity (nominal) not over 125 pounds water capacity (nominal) and a service pressure at least 150 to not over 500 pounds per square inch. (b) Nickel. The percentage of nickel plus cobalt must be at least 99.0 percent. (c) Identification of material. The material must be identified by any suitable method except that plates and billets for hot-drawn cylinders must be marked with the heat number. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. Cylinders closed in by spinning process are not authorized. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited except that welding is authorized for the attachment of neckrings and footrings which are nonpressure parts, and only to the tops and bottoms of cylinders. Neckrings and footrings must be of weldable material, the carbon content of which may not exceed 0.25 percent. Nickel welding rod must be used. (f) Wall thickness. The wall stress may not exceed 15,000 pounds per square inch. A minimum wall thickness of 0.100 inch is required for any cylinder over 5 inches in outside diameter. Wall stress calculation must be made by using the following formula: S=[P(1.3D\2\+0.4d\2\)]/(D\2\-d\2\) Where: S=wall stress in pounds per square inch; P=minimum test pressure prescribed for water jacket test or 450 pounds per square inch whichever is the greater; D=outside diameter in inches; d=inside diameter in inches. (g) Heat treatment. The completed cylinders must be uniformly and properly heat-treated prior to tests. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings: (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, to be of length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must successfully withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. The pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent or 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer [[Page 25950]] to ensure complete expansion. Any internal pressure applied after heat- treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, whichever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least 2 times service pressure. (j) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (k) Physical test. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) The test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of 200 or less. For lots of 30 or less, physical tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (2) Specimens must conform to the following: (i) A gauge length of 8 inches with a width of not over 1\1/2\ inches, a gauge length of 2 inches with a width of not over 1\1/2\ inches, or a gauge length of at least 24 times the thickness with a width not over 6 times thickness is authorized when a cylinder wall is not over \3/16\ inch thick. (ii) The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. (iii) When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold, by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with record of physical tests detailed information in regard to such specimens. (iv) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. The following conditions apply: (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, and the strain indicator reading must be set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (l) Acceptable results for physical and flattening tests. Either of the following is an acceptable result: (1) An elongation of at least 40 percent for a 2 inch gauge length or at least 20 percent in other cases and yield point not over 50 percent of tensile strength. In this instance, the flattening test is not required. (2) An elongation of at least 20 percent for a 2 inch gauge length or 10 percent in other cases and a yield point not over 50 percent of tensile strength. Flattening is required, without cracking, to 6 times the wall thickness. (m) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding is not authorized. Sec. 178.42 Specification 3E seamless steel cylinders. (a) Type, size, and service pressure. A DOT 3E cylinder is a seamless steel cylinder with an outside diameter not greater than 2 inches nominal, a length less than 2 feet and a service pressure of 1,800 pounds per square inch. (b) Steel. Open-hearth or electric steel of uniform quality must be used. Content percent may not exceed the following: Carbon, 0.55; phosphorus, 0.045; sulphur, 0.050. (c) Identification of steel. Materials must be identified by any suitable method. (d) Manufacture. Cylinders must be manufactured by best appliances and methods. No defect is permitted that is likely to weaken the finished cylinder appreciably. A reasonably smooth and uniform surface finish is required. The thickness of the spun bottom is, under no condition, to be less than two times the minimum wall thickness of the cylindrical shell; such bottom thickness must be measured within an area bounded by a line representing the points of contact between the cylinder and floor when the cylinder is in a vertical position. (e) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings. (1) Threads must be clean cut, even, without checks, and to gauge. (2) Taper threads, when used, must be of length not less than as specified for American Standard taper pipe threads. (3) Straight threads having at least 4 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear strength of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (f) Hydrostatic test. Cylinders must be tested as follows: (1) One cylinder out of each lot of 500 or less must be subjected to a hydrostatic pressure of 6,000 pounds per square inch or higher. (2) The cylinder referred to in paragraph (f)(1) of this section must burst at a pressure higher than 6,000 pounds per square inch without fragmenting or otherwise showing lack of ductility, or must hold a pressure of 12,000 pounds per square inch for 30 seconds without bursting. In which case, it must be subjected to a flattening test without cracking to six times wall thickness between knife edges, wedge shaped 60 degree angle, rounded out to a \1/2\ inch radius. The inspector's report must be suitably changed to show results of latter alternate and flattening test. (3) Other cylinders must be examined under pressure of at least 3,000 pounds per square inch and not to exceed 4,500 pounds per square inch and show no defect. Cylinders tested at a pressure in excess of 3,600 pounds per square inch must burst at a pressure higher than 7,500 pounds per square inch when tested as specified in paragraph (f)(2) of this section. The pressure must be maintained for at least 30 seconds and [[Page 25951]] sufficiently longer to ensure complete examination. (g) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by gas or air pressure after the bottom has been cleaned and is free from all moisture subject to the following conditions and limitations: (1) A pressure, approximately the same as but not less than the service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Accept as provided in paragraph (h) of this section, a cylinder must be rejected if there is any leakage. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer shall design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (h) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. Spun cylinders rejected under the provisions of paragraph (g) of this section may be removed from the spun cylinder category by drilling to remove defective material, tapping and plugging. (i) Marking. Markings required by Sec. 178.35 must be stamped plainly and permanently on the shoulder, top head, neck or sidewall of each cylinder. Sec. 178.44 Specification 3HT seamless steel cylinders for aircraft use. (a) Type, size and service pressure. A DOT 3HT cylinder is a seamless steel cylinder with a water capacity (nominal) of not over 150 pounds and a service pressure of at least 900 pounds per square inch. (b) Authorized steel. Open hearth or electric furnace steel of uniform quality must be used. A heat of steel made under the specifications listed in Table 1 in this paragraph (b), check chemical analysis of which is slightly out of the specified range, is acceptable, if satisfactory in all other respects, provided the tolerances shown in Table 2 in this paragraph (b) are not exceeded. Grain size 6 or finer according to ASTM E 112. Steel of the following chemical analysis is authorized: Table 1.--Authorized Materials ------------------------------------------------------------------------ Designation AISI 4130 (percent) ------------------------------------------------------------------------ Carbon....................................... 0.28/0.33 Manganese.................................... 0.40/0.60 Phosphorus................................... 0.040 maximum Sulfur....................................... 0.040 maximum Silicon...................................... 0.15/0.35 Chromium..................................... 0.80/1.10 Molybdenum................................... 0.18/0.25 ------------------------------------------------------------------------ Table 2.--Check Analysis Tolerances ---------------------------------------------------------------------------------------------------------------- Tolerance (percent) over the maximum limit or under the minimum limit Element Limit or maximum specified (percent) ------------------------- Under Over minimum maximum limit limit ---------------------------------------------------------------------------------------------------------------- Carbon......................... Over 0.15 to 0.40 incl............................... .03 .04 Manganese...................... To 0.60 incl......................................... .03 .03 Phosphorus\1\.................. All ranges........................................... ........... .01 Sulphur........................ All ranges........................................... ........... .01 Silicon........................ To 0.30 incl......................................... .02 .03 Over 0.30 to 1.00 incl............................... .05 .05 Chromium....................... To 0.90 incl......................................... .03 .03 Over 0.90 to 2.10 incl............................... .05 .05 Molybdenum..................... To 0.20 incl......................................... .01 .01 Over 0.20 to 0.40 incl............................... .02 .02 ---------------------------------------------------------------------------------------------------------------- \1\ Rephosphorized steels not subject to check analysis for phosphorus. (c) Identification of material. Material must be identified by any suitable method. Steel stamping of heat identifications may not be made in any area which will eventually become the side wall of the cylinder. Depth of stamping may not encroach upon the minimum prescribed wall thickness of the cylinder. (d) Manufacture. Cylinders must be manufactured using equipment and processes adequate to ensure that each cylinder produced conforms to the requirements of this subpart. No fissure or other defect is permitted that is likely to weaken the finished container appreciably. The general surface finish may not exceed a roughness of 250 RMS. Individual irregularities such as draw marks, scratches, pits, etc., should be held to a minimum consistent with good high stress pressure vessel manufacturing practices. If the cylinder is not originally free of such defects or does not meet the finish requirements, the surface may be machined or otherwise treated to eliminate these [[Page 25952]] defects. The point of closure of cylinders closed by spinning may not be less than two times the prescribed wall thickness of the cylindrical shell. The cylinder end contour must be hemispherical or ellipsoidal with a ratio of major-to-minor axis not exceeding two to one and with the concave side to pressure. (e) Welding or brazing. Welding or brazing for any purpose whatsoever is prohibited, except that welding by spinning is permitted to close the bottom of spun cylinders. Machining or grinding to produce proper surface finish at point of closure is required. (f) Wall thickness. (1) Minimum wall thickness for any cylinder must be 0.050 inch. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure may not exceed 75 percent of the minimum tensile strength of the steel as determined from the physical tests required in paragraph (m) of this section and may not be over 105,000 psi. (2) Calculations must be made by the formula: S=[P(1.3D\2\+0.4d\2\)]/(D\2\-d\2\) Where: S=Wall stress in pounds per square inch; P=Minimum test pressure prescribed for water jacket test; D=Outside diameter in inches; d=Inside diameter in inches. (3) Wall thickness of hemispherical bottoms only permitted to 90 percent of minimum wall thickness of cylinder sidewall but may not be less than 0.050 inch. In all other cases, thickness to be no less than prescribed minimum wall. (g) Heat treatment. The completed cylinders must be uniformly and properly heated prior to tests. Heat treatment of the cylinders of the authorized analysis must be as follows: (1) All cylinders must be quenched by oil, or other suitable medium. (2) The steel temperature on quenching must be that recommended for the steel analysis, but may not exceed 1750 deg.F. (3) The steel must be tempered at a temperature most suitable for the particular steel analysis but not less than 850 deg.F. (4) All cylinders must be inspected by the magnetic particle or dye penetrant method to detect the presence of quenching cracks. Any cylinder found to have a quenching crack must be rejected and may not be requalified. (h) Openings in cylinders and connections (valves, fuse plugs, etc.) for those openings. Threads conforming to the following are required on openings: (1) Threads must be clean cut, even, without cracks, and to gauge. (2) Taper threads, when used, must be of length not less than as specified for National Gas Tapered Thread (NGT) as required by American Standard Compressed Gas Cylinder Valve Outlet and Inlet Connections. (3) Straight threads having at least 6 engaged threads are authorized. Straight threads must have a tight fit and a calculated shear stress of at least 10 times the test pressure of the cylinder. Gaskets, adequate to prevent leakage, are required. (i) Hydrostatic test. Each cylinder must withstand a hydrostatic test, as follows: (1) The test must be by water-jacket, or other suitable method, operated so as to obtain accurate data. Pressure gauge must permit reading to an accuracy of 1 percent. The expansion gauge must permit reading of total expansion to an accuracy either of 1 percent of 0.1 cubic centimeter. (2) Pressure must be maintained for at least 30 seconds and sufficiently longer to ensure complete expansion. Any internal pressure applied after heat treatment and previous to the official test may not exceed 90 percent of the test pressure. If, due to failure of the test apparatus, the test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 pounds per square inch, which ever is the lower. (3) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (4) Each cylinder must be tested to at least \5/3\ times service pressure. (j) Cycling tests. Prior to the initial shipment of any specific cylinder design, cyclic pressurization tests must have been performed on at least three representative samples without failure as follows: (1) Pressurization must be performed hydrostatically between approximately zero psig and the service pressure at a rate not in excess of 10 cycles per minute. Adequate recording instrumentation must be provided if equipment is to be left unattended for periods of time. (2) Tests prescribed in paragraph (j)(1) of this section must be repeated on one random sample out of each lot of cylinders. The cylinder may then be subjected to a burst test. (3) A lot is defined as a group of cylinders fabricated from the same heat of steel, manufactured by the same process and heat treated in the same equipment under the same conditions of time, temperature, and atmosphere, and may not exceed a quantity of 200 cylinders. (4) All cylinders used in cycling tests must be destroyed. (k) Burst test. One cylinder taken at random out of each lot of cylinders must be hydrostatically tested to destruction. (l) Flattening test. A flattening test must be performed on one cylinder taken at random out or each lot of 200 or less, by placing the cylinder between wedge shaped knife edges having a 60 deg. included angle, rounded to \1/2\-inch radius. The longitudinal axis of the cylinder must be at a 90-degree angle to knife edges during the test. For lots of 30 or less, flattening tests are authorized to be made on a ring at least 8 inches long cut from each cylinder and subjected to same heat treatment as the finished cylinder. (m) Physical tests. A physical test must be conducted to determine yield strength, tensile strength, elongation, and reduction of area of material, as follows: (1) Test is required on 2 specimens cut from 1 cylinder taken at random out of each lot of cylinders. (2) Specimens must conform to the following: (i) A gauge length of at least 24 times the thickness with a width not over six times the thickness. The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. When size of cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When specimens are so taken and prepared, the inspector's report must show in connection with the record of physical tests detailed information in regard to such specimens. (ii) Heating of a specimen for any purpose is not authorized. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard E8. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. In the event of controversy, [[Page 25953]] the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 12,000 pounds per square inch, the strain indicator reading being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (n) Magnetic particle inspection. Inspection must be performed on the inside of each container before closing and externally on each finished container after heat treatment. Evidence of discontinuities, which in the opinion of a qualified inspector may appreciably weaken or decrease the durability of the cylinder, must be cause for rejection. (o) Leakage test. All spun cylinders and plugged cylinders must be tested for leakage by dry gas or dry air pressure after the bottom has been cleaned and is free from all moisture, subject to the following conditions and limitations: (1) Pressure, approximately the same as but not less than service pressure, must be applied to one side of the finished bottom over an area of at least \1/16\ of the total area of the bottom but not less than \3/4\ inch in diameter, including the closure, for at least one minute, during which time the other side of the bottom exposed to pressure must be covered with water and closely examined for indications of leakage. Except as provided in paragraph (q) of this section, a cylinder must be rejected if there is leakage. (2) A spun cylinder is one in which an end closure in the finished cylinder has been welded by the spinning process. (3) A plugged cylinder is one in which a permanent closure in the bottom of a finished cylinder has been effected by a plug. (4) As a safety precaution, if the manufacturer elects to make this test before the hydrostatic test, the manufacturer should design the test apparatus so that the pressure is applied to the smallest area practicable, around the point of closure, and so as to use the smallest possible volume of air or gas. (p) Acceptable results of tests. Results of the flattening test, physical tests, burst test, and cycling test must conform to the following: (1) Flattening required without cracking to ten times the wall thickness of the cylinder. (2) Physical tests: (i) An elongation of at least 6 percent for a gauge length of 24 times the wall thickness. (ii) The tensile strength may not exceed 165,000 p.s.i. (3) The burst pressure must be at least \4/3\ times the test pressure. (4) Cycling-at least 10,000 pressurizations. (q) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. Repair by welding or spinning is not authorized. For each cylinder subjected to reheat treatment during original manufacture, sidewall measurements must be made to verify that the minimum sidewall thickness meets specification requirements after the final heat treatment. (r) Marking. (1) Cylinders must be marked by low stress type steel stamping in an area and to a depth which will insure that the wall thickness measured from the root of the stamping to the interior surface is equal to or greater than the minimum prescribed wall thickness. Stamping must be permanent and legible. Stamping on side wall not authorized. (2) The rejection elastic expansion (REE), in cubic centimeters (cc), must be marked on the cylinder near the date of test. The REE for a cylinder is 1.05 times its original elastic expansion. (3) Name plates are authorized, provided that they can be permanently and securely attached to the cylinder. Attachment by either brazing or welding is not permitted. Attachment by soldering is permitted provided steel temperature does not exceed 500 deg.F. (s) Inspector's report. In addition to the requirements of Sec. 178.35, the inspector's report must indicate the rejection elastic expansion (REE), in cubic centimeters (cc). Sec. 178.45 Specification 3T seamless steel cylinder. (a) Type, size, and service pressure. A DOT 3T cylinder is a seamless steel cylinder with a minimum water capacity of 1,000 pounds and a minimum service pressure of 1,800 p.s.i. Each cylinder must have integrally formed heads concave to pressure at both ends. The inside head shape must be hemispherical, ellipsoidal in which the major axis is two times the minor axis, or a dished shape falling within these two limits. Permanent closures formed by spinning are prohibited. (b) Material, steel. Only open hearth, basic oxygen, or electric furnace process steel of uniform quality is authorized. The steel analysis must conform to the following: Analysis Tolerances ------------------------------------------------------------------------ Check Analysis Element Ladle analysis --------------------- Under Over ------------------------------------------------------------------------ Carbon...................... 0.35 to 0.50........ 0.03 0.04 Manganese................... 0.75 to 1.05........ 0.04 0.04 Phosphorus (max)............ 0.035............... ......... 0.01 Sulphur (max)............... 0.04................ ......... 0.01 Silicon..................... 0.15 to 0.35........ 0.02 0.03 Chromium.................... 0.80 to 1.15........ 0.05 0.05 Molybdenum.................. 0.15 to 0.25........ 0.02 0.02 ------------------------------------------------------------------------ (1) A heat of steel made under the specifications in the table in this paragraph (b), the ladle analysis of which is slightly out of the specified range, is acceptable if satisfactory in all other aspects. However, the check analysis tolerances shown in the table in this paragraph (b) may not be exceeded except as approved by the Department. (2) Material with seams, cracks, laminations, or other injurious defects is not permitted. (3) Material used must be identified by any suitable method. (c) Manufacture. General manufacturing requirements are as follows: (1) Surface finish must be uniform and reasonably smooth. (2) Inside surfaces must be clean, dry, and free of loose particles. [[Page 25954]] (3) No defect of any kind is permitted if it is likely to weaken a finished cylinder. (4) If the cylinder surface is not originally free from the defects, the surface may be machined or otherwise treated to eliminate these defects provided the minimum wall thickness is maintained. (5) Welding or brazing on a cylinder is not permitted. (d) Wall thickness. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure does not exceed 67 percent of the minimum tensile strength of the steel as determined by the physical tests required in paragraphs (j) and (k) of this section. A wall stress of more than 90,500 p.s.i. is not permitted. The minimum wall thickness for any cylinder may not be less than 0.225 inch. (1) Calculation of the stress for cylinders must be made by the following formula: S=[P(1.3D2+0.4d2)]/(D2-d2) Where: S=Wall stress in pounds per square inch; P=Minimum test pressure, at least \5/3\ service pressure; D=Outside diameter in inches; d=Inside diameter in inches. (2) Each cylinder must meet the following additional requirement which assumes a cylinder horizontally supported at its two ends and uniformly loaded over its entire length. This load consists of the weight per inch of length of the straight cylindrical portion filled with water compressed to the specified test pressure. The wall thickness must be increased when necessary to meet this additional requirement: (i) The sum of two times the maximum tensile stress in the bottom fibers due to bending (see paragraph (d)(2)(ii) of this section), plus the maximum tensile stress in the same fibers due to hydrostatic testing (see paragraph (d)(2)(iii) of this section) may not exceed 80 percent of the minimum yield strength of the steel at this maximum stress. (ii) The following formula must be used to calculate the maximum tensile stress due to bending: S=Mc/I Where: S=Tensile stress in pounds per square inch; M=Bending moment in inch-pounds (wl2/8); I=Moment of inertia--0.04909 (D4-d4) in inches fourth; c=Radius (D/2) of cylinder in inches; w=Weight per inch of cylinder filled with water; l=Length of cylinder in inches; D=Outside diameter in inches; d=Inside diameter in inches. (iii) The following formula must be used to calculate the maximum longitudinal tensile stress due to hydrostatic test pressure: S=A1P/A2 Where: S=Tensile stress in pounds per square inch; A1=Internal area in cross section of cylinder in square inches; P=Hydrostatic test pressure in pounds per square, inch; A2=Area of metal in cross section of cylinder in square inches. (e) Heat treatment. Each completed cylinder must be uniformly and properly heat treated prior to testing, as follows: (1) Each cylinder must be heated and held at the proper temperature for at least one hour per inch of thickness based on the maximum thickness of the cylinder and then quenched in a suitable liquid medium having a cooling rate not in excess of 80 percent of water. The steel temperature on quenching must be that recommended for the steel analysis, but it must never exceed 1750 deg.F. (2) After quenching, each cylinder must be reheated to a temperature below the transformation range but not less than 1050 deg.F., and must be held at this temperature for at least one hour per inch of thickness based on the maximum thickness of the cylinder. Each cylinder must then be cooled under conditions recommended for the steel. (f) Openings. Openings in cylinders must comply with the following: (1) Openings are permitted on heads only. (2) The size of any centered opening in a head may not exceed one half the outside diameter of the cylinder. (3) Openings in a head must have ligaments between openings of at least three times the average of their hole diameter. No off-center opening may exceed 2.625 inches in diameter. (4) All openings must be circular. (5) All openings must be threaded. Threads must be in compliance with the following: (i) Each thread must be clean cut, even, without any checks, and to gauge. (ii) Taper threads, when used, must be the American Standard Pipe thread (NPT) type and must be in compliance with the requirements of NBS Handbook H-28, Part II, Section VII. (iii) Taper threads conforming to National Gas Taper thread (NGT) standards must be in compliance with the requirements of NBS Handbook H-28, Part II, Sections VII and IX. (iv) Straight threads conforming with National Gas Straight thread (NGS) standards are authorized. These threads must be in compliance with the requirements of NBS Handbook H-28, Part II, Sections VII and IX. (g) Hydrostatic test. Each cylinder must be tested at an internal pressure by the water jacket method or other suitable method, conforming to the following requirements: (1) The testing apparatus must be operated in a manner that will obtain accurate data. Any pressure gauge used must permit reading to an accuracy of one percent. Any expansion gauge used must permit reading of the total expansion to an accuracy of one percent. (2) Any internal pressure applied to the cylinder after heat treatment and before the official test may not exceed 90 percent of the test pressure. (3) The pressure must be maintained sufficiently long to assure complete expansion of the cylinder. In no case may the pressure be held less than 30 seconds. (4) If, due to failure of the test apparatus, the required test pressure cannot be maintained, the test must be repeated at a pressure increased by 10 percent or 100 p.s.i., whichever is lower or, the cylinder must be reheat treated. (5) Permanent volumetric expansion of the cylinder may not exceed 10 percent of its total volumetric expansion at the required test pressure. (6) Each cylinder must be tested to at least \5/3\ times its service pressure. (h) Ultrasonic examination. After the hydrostatic test, the cylindrical section of each vessel must be examined in accordance with ASTM Standard A-388-67 using the angle beam technique. The equipment used must be calibrated to detect a notch equal to five percent of the design minimum wall thickness. Any discontinuity indication greater than that produced by the five percent notch must be cause for rejection of the cylinder unless the discontinuity is repaired within the requirements of this specification. (i) Basic requirements for tension and Charpy impact tests. Cylinders must be subjected to a tension and Charpy impact as follows: (1) When the cylinders are heat treated in a batch furnace, two tension specimens and three Charpy impact specimens must be tested from one of the cylinders or a test ring from each batch. The lot size represented by these tests may not exceed 200 cylinders. [[Page 25955]] (2) When the cylinders are heat treated in a continuous furnace, two tension specimens and three Charpy impact specimens must be tested from one of the cylinders or a test ring from each four hours or less of production. However, in no case may a test lot based on this production period exceed 200 cylinders. (3) Each specimen for the tension and Charpy impact tests must be taken from the side wall of a cylinder or from a ring which has been heat treated with the finished cylinders of which the specimens must be representative. The axis of the specimens must be parallel to the axis of the cylinder. Each cylinder or ring specimen for test must be of the same diameter, thickness, and metal as the finished cylinders they represent. A test ring must be at least 24 inches long with ends covered during the heat treatment process so as to simulate the heat treatment process of the finished cylinders it represents. (4) A test cylinder or test ring need represent only one of the heats in a furnace batch provided the other heats in the batch have previously been tested and have passed the tests and that such tests do not represent more than 200 cylinders from any one heat. (5) The test results must conform to the requirements specified in paragraphs (j) and (k) of this section. (6) When the test results do not conform to the requirements specified, the cylinders represented by the tests may be reheat treated and the tests repeated. Paragraph (i)(5) of this section applies to any retesting. (j) Basic conditions for acceptable physical testing. The following criteria must be followed to obtain acceptable physical test results: (1) Each tension specimen must have a gauge length of two inches with a width not exceeding one and one-half inches. Except for the grip ends, the specimen may not be flattened. The grip ends may be flattened to within one inch of each end of the reduced section. (2) A specimen may not be heated after heat treatment specified in paragraph (d) of this section. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gage length. (i) This yield strength must be determined by the ``offset'' method or the ``extension under load'' method described in ASTM Standard E8. (ii) For the ``extension under load'' method, the total strain (or extension under load) corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gage length under appropriate load and adding thereto 0.2 percent of the gage length. Elastic extension calculations must be based on an elastic modulus of 30,000,000. However, when the degree of accuracy of this method is questionable the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set with the specimen under a stress of 12,000 p.s.i. and the strain indicator reading set at the calculated corresponding strain. (iv) The cross-head speed of the testing machine may not exceed \1/ 8\ inch per minute during the determination of yield strength. (4) Each impact specimen must be Charpy V-notch type size 10 mm x 10 mm taken in accordance with paragraph 11 of ASTM Standard A-333-67. When a reduced size specimen is used, it must be the largest size obtainable. (k) Acceptable physical test results. Results of physical tests must conform to the following: (1) The tensile strength may not exceed 155,000 p.s.i. (2) The elongation must be at least 16 percent for a two-inch gage length. (3) The Charpy V-notch impact properties for the three impact specimens which must be tested at 0 deg.F may not be less than the values shown as follows: ------------------------------------------------------------------------ Average value for Minimum value (1 Size of specimen (mm) acceptance (3 specimen only of the specimens) 3) ------------------------------------------------------------------------ 10.0x10.0................... 25.0 ft. lbs........ 20.0 ft. lbs. 10.0x7.5.................... 21.0 ft. lbs........ 17.0 ft. lbs. 10.0x5.0.................... 17.0 ft. lbs........ 14.0 ft. lbs. ------------------------------------------------------------------------ (4) After the final heat treatment, each vessel must be hardness tested on the cylindrical section. The tensile strength equivalent of the hardness number obtained may not be more than 165,000 p.s.i. (Rc 36). When the result of a hardness test exceeds the maximum permitted, two or more retests may be made; however, the hardness number obtained in each retest may not exceed the maximum permitted. (l) Rejected cylinders. Reheat treatment is authorized for rejected cylinders. However, each reheat treated cylinder must subsequently pass all the prescribed tests. Repair by welding is not authorized. (m) Markings. Marking must be done by stamping into the metal of the cylinder. All markings must be legible and located on a shoulder. (n) Inspector's report. In addition to the requirements of Sec. 178.35, the inspector's report for the physical test report, must indicate the average value for three specimens and the minimum value for one specimen for each lot number. Sec. 178.46 Specification 3AL seamless aluminum cylinders. (a) Size and service pressure. A DOT 3AL cylinder is a seamless aluminum cylinder with a maximum water capacity of 1000 pounds and minimum service pressure of 150 psig. (b) Authorized material and identification of material. The material of construction must meet the following conditions: (1) Starting stock must be cast stock or traceable to cast stock. (2) Material with seams, cracks, laminations, or other defects likely to weaken the finished cylinder may not be used. (3) Material must be identified by a suitable method that will identify the alloy, the aluminum producer's cast number, the solution heat treat batch number and the lot number. (4) The material must be of uniform quality. Only the following heat treatable aluminum alloys in Table 1 and 2 are permitted as follows: [[Page 25956]] Table 1.--Chemical Composition Limits [Chemical composition (in weight percent)] -------------------------------------------------------------------------------------------------------------------------------------------------------- Other \1\ Aluminum Assoc. alloy Si Fe Cu Mn Mg Cr Zn Ti Pb Bi -------------- A1 designation No. Each Total -------------------------------------------------------------------------------------------------------------------------------------------------------- 6351........................... 0.7-1.3 0.50 0.10 0.40-0.80 0.40-0.80 ......... 0.20 0.20 0.01 0.01 0.05 0.15 Remainder. 6061........................... 0.40-0.80 0.70 0.15-0.40 0.15 0.80-1.20 0.04-0.35 0.25 0.15 0.01 0.01 0.05 0.15 Remainder. -------------------------------------------------------------------------------------------------------------------------------------------------------- \1\ Analysis is regularly made only for the elements for which specific limits are shown, except for unalloyed aluminum. If, however, the presence of other elements is suspected to be, or in the course of routine analysis is indicated to be in excess of specified limits, further analysis is made to determine that these other elements are not in excess of the amounts specified. (Aluminum Association Standards and Data.) Table 2.--Mechanical Property Limits ---------------------------------------------------------------------------------------------------------------- Tensile strength--PSI --------------------------------- Elongation--percent Alloy and temper Yield-- minimum for 2'' or Ultimate--minimum minimum 4D \1\ size ---------------------------------------------------------------------------------------------------specimen----- 6351-T6................................................... 42,000 37,000 \2\14 6061-T6................................................... 38,000 35,000 \2\14 ---------------------------------------------------------------------------------------------------------------- \1\ ``D'' represents specimen diameters. When the cylinder wall is greater than \3/16\ inch thick, a retest without reheat treatment using the 4D size specimen is authorized if the test using the 2 inch size specimen fails to meet elongation requirements. \2\ When cylinder wall is not over \3/16\-inch thick, 10 percent elongation is authorized when using a 24t x 6t size test specimen. (5) All starting stock must be 100 percent ultrasonically inspected, along the length at right angles to the central axis from two positions at 90 deg. to one another. The equipment and continuous scanning procedure must be capable of detecting and rejecting internal defects such as cracks which have an ultrasonic response greater than that of a calibration block with a \5/64\-inch diameter flat bottomed hole. (6) Cast stock must have uniform equiaxed grain structure not to exceed 500 microns maximum. (7) Any starting stock not complying with the provisions of paragraphs (b)(1) through (b)(6) of this section must be rejected. (c) Manufacture. Cylinders must be manufactured in accordance with the following requirements: (1) Cylinder shells must be manufactured by the backward extrusion method and have a cleanliness level adequate to ensure proper inspection. No fissure or other defect is acceptable that is likely to weaken the finished cylinder below the design strength requirements. A reasonably smooth and uniform surface finish is required. If not originally free from such defects, the surface may be machined or otherwise conditioned to eliminate these defects. (2) Thickness of the cylinder base may not be less than the prescribed minimum wall thickness of the cylindrical shell. The cylinder base must have a basic torispherical, hemispherical, or ellipsoidal interior base configuration where the dish radius is no greater than 1.2 times the inside diameter of the shell. The knuckle radius may not be less than 12 percent of the inside diameter of the shell. The interior base contour may deviate from the true torispherical, hemispherical or ellipsoidal configuration provided that-- (i) Any areas of deviation are accompanied by an increase in base thickness; (ii) All radii of merging surfaces are equal to or greater than the knuckle radius; (iii) Each design has been qualified by successfully passing the cycling tests in this paragraph (c); and (iv) Detailed specifications of the base design are available to the inspector. (3) For free standing cylinders, the base thickness must be at least two times the minimum wall thickness along the line of contact between the cylinder base and the floor when the cylinders are in the vertical position. (4) Welding or brazing is prohibited. (5) Each new design and any significant change to any acceptable design must be qualified for production by testing prototype samples as follows: (i) Three samples must be subjected to 100,000 pressure reversal cycles between zero and service pressure or 10,000 pressure reversal cycles between zero and test pressure, at a rate not in excess of 10 cycles per minute without failure. (ii) Three samples must be pressurized to destruction and failure may not occur at less than 2.5 times the marked cylinder service pressure. Each cylinder must remain in one piece. Failure must initiate in the cylinder sidewall in a longitudinal direction. Rate of pressurization may not exceed 200 psi per second. (6) In this specification ``significant change'' means a 10 percent or greater change in cylinder wall thickness, service pressure, or diameter; a 30 percent or greater change in water capacity or base thickness; any change in material; over 100 percent increase in size of openings; or any change in the number of openings. (d) Wall thickness. The minimum wall thickness must be such that the wall stress at the minimum specified test pressure will not exceed 80 percent of the minimum yield strength nor exceed 67 percent of the minimum ultimate tensile strength as verified by physical tests in paragraph (i) of this section. The minimum wall thickness for any cylinder with an outside diameter greater than 5 inches must be 0.125 inch. Calculations must be made by the following formula: S=[P(1.3D\2\+0.4d\2\)]/(D\2\-d\2\) Where: S=Wall stress in pounds per square inch; P=Prescribed minimum test pressure in pounds per square inch (see paragraph (g) of this section); D=Outside diameter in inches; and d=Inside diameter in inches. (e) Openings. Openings must comply with the following requirements: (1) Openings are permitted in heads only. (2) The size of any centered opening in a head may not exceed one- half the outside diameter of the cylinder. (3) Other openings are permitted in the head of a cylinder if: (i) Each opening does not exceed 2.625 inches in diameter, or one- half the outside diameter of the cylinder; whichever is less; [[Page 25957]] (ii) Each opening is separated from each other by a ligament; and (iii) Each ligament which separates two openings must be at least three times the average of the diameters of the two openings. (4) All openings must be circular. (5) All openings must be threaded. Threads must comply with the following: (i) Each thread must be clean cut, even, without checks, and to gauge. (ii) Taper threads, when used, must conform to one of the following: (A) American Standard Pipe Thread (NPT) type, conforming to the requirements of Federal Standard H-28, Section 7; (B) National Gas Taper Thread (NGT) type, conforming to the requirements of Federal Standard H-28, Sections 7 and 9; or (C) Other taper threads conforming to other standards may be used provided the length is not less than that specified for NPT threads. (iii) Straight threads, when used, must conform to one of the following: (A) National Gas Straight Thread (NGS) type, conforming to the requirements of Federal Standard H-28, Sections 7 and 9; (B) Unified Thread (UN) type, conforming to the requirements of Federal Standard H-28, Section 2; (C) Controlled Radius Root Thread (UN) type, conforming to the requirements of Federal Standard H-28, Section 4; or (D) Other straight threads conforming to other recognized standards may be used provided that the requirements in paragraph (e)(5)(iv) of this section are met. (iv) All straight threads must have at least 6 engaged threads, a tight fit, and a factor of safety in shear of at least 10 at the test pressure of the cylinder. Shear stress must be calculated by using the appropriate thread shear area in accordance with Federal Standard H-28, Appendix A5, Section 3. (f) Heat treatment. Prior to any test, all cylinders must be subjected to a solution heat treatment and aging treatment appropriate for the aluminum alloy used. (g) Hydrostatic test. Each cylinder must be subjected to an internal test pressure using the water jacket equipment and method or other suitable equipment and method and comply with the following requirements: (1) The testing apparatus must be operated in a manner so as to obtain accurate data. The pressure gauge used must permit reading to an accuracy of one percent. The expansion gauge must permit reading the total expansion to an accuracy of either one percent or 0.1 cubic centimeter. (2) The test pressure must be maintained for a sufficient period of time to assure complete expansion of the cylinder. In no case may the pressure be held less than 30 seconds. If, due to failure of the test apparatus, the required test pressure cannot be maintained, the test may be repeated at a pressure increased by 10 percent or 100 psi, whichever is lower. If the test apparatus again fails to maintain the test pressure, the cylinder being tested must be rejected. Any internal pressure applied to the cylinder before any official test may not exceed 90 percent of the test pressure. (3) The minimum test pressure is the greatest of the following: (i) 450 psi regardless of service pressure; (ii) Two times the service pressure for cylinders having service pressure less than 500 psi; or (iii) Five-thirds times the service pressure for cylinders having a service pressure of at least 500 psi. (4) Permanent volumetric expansion may not exceed 10 percent of total volumetric expansion at test pressure. (h) Flattening test. One cylinder taken at random out of each lot must be subjected to a flattening test as follows: (1) The test must be between knife edges, wedge shaped, having a 60 deg. included angle, and rounded in accordance with the following table. The longitudinal axis of the cylinder must be at an angle 90 deg. to the knife edges during the test. The flattening test table is as follows: Table 3.--Flattening Test Table ------------------------------------------------------------------------ Radius Cylinder wall thickness in inches in inches ------------------------------------------------------------------------ Under .150.................................................... .500 .150 to .249.................................................. .875 .250 to .349.................................................. 1.500 .350 to .449.................................................. 2.125 .450 to .549.................................................. 2.750 .550 to .649.................................................. 3.500 .650 to .749.................................................. 4.125 ------------------------------------------------------------------------ (2) An alternate bend test in accordance with ASTM E 290 using a mandrel diameter not more than 6 times the wall thickness is authorized to qualify lots that fail the flattening test of this section without reheat treatment. If used, this test must be performed on two samples from one cylinder taken at random out of each lot of 200 cylinders or less. (3) Each test cylinder must withstand flattening to nine times the wall thickness without cracking. When the alternate bend test is used, the test specimens must remain uncracked when bent inward around a mandrel in the direction of curvature of the cylinder wall until the interior edges are at a distance apart not greater than the diameter of the mandrel. (i) Mechanical properties test. Two test specimens cut from one cylinder representing each lot of 200 cylinders or less must be subjected to the mechanical properties test, as follows: (1) The results of the test must conform to at least the minimum acceptable mechanical property limits for aluminum alloys as specified in paragraph (b) of this section. (2) Specimens must be 4D bar or gauge length 2 inches with width not over 1\1/2\ inch taken in the direction of extrusion approximately 180 deg. from each other; provided that gauge length at least 24 times thickness with width not over 6 times thickness is authorized, when cylinder wall is not over \3/16\ inch thick. The specimen, exclusive of grip ends, may not be flattened. Grip ends may be flattened to within one inch of each end of the reduced section. When the size of the cylinder does not permit securing straight specimens, the specimens may be taken in any location or direction and may be straightened or flattened cold by pressure only, not by blows. When such specimens are used, the inspector's report must show that the specimens were so taken and prepared. Heating of specimens for any purpose is forbidden. (3) The yield strength in tension must be the stress corresponding to a permanent strain of 0.2 percent of the gauge length. (i) The yield strength must be determined by either the ``offset'' method or the ``extension under load'' method as prescribed in ASTM Standard B-557. (ii) In using the ``extension under load'' method, the total strain (or ``extension under load'') corresponding to the stress at which the 0.2 percent permanent strain occurs may be determined with sufficient accuracy by calculating the elastic extension of the gauge length under appropriate load and adding thereto 0.2 percent of the gauge length. Elastic extension calculations must be based on an elastic modulus of 10,000,000 psi. In the event of controversy, the entire stress-strain diagram must be plotted and the yield strength determined from the 0.2 percent offset. (iii) For the purpose of strain measurement, the initial strain must be set while the specimen is under a stress of 6,000 psi, the strain indicator reading [[Page 25958]] being set at the calculated corresponding strain. (iv) Cross-head speed of the testing machine may not exceed \1/8\ inch per minute during yield strength determination. (j) Rejected cylinder. Reheat treatment of rejected cylinders is authorized one time. Subsequent thereto, cylinders must pass all prescribed tests to be acceptable. (k) Duties of inspector. In addition to the requirements of Sec. 178.35, the inspector shall: (1) Verify compliance with the provisions of paragraph (b) of this section by: (i) Performing or witnessing the performance of the chemical analyses on each melt or cast lot or other unit of starting material; or (ii) Obtaining a certified chemical analysis from the material or cylinder manufacturer for each melt, or cast of material; or (iii) Obtaining a certified check analysis on one cylinder out of each lot of 200 cylinders or less, if a certificate containing data to indicate compliance with the material specification is obtained. (2) The inspector shall verify ultrasonic inspection of all material by ins [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A96-12029. Public record. Not legal advice.